Enhanced adsorption of acetylsalicylic acid over hydrothermally synthesized iron oxide-mesoporous silica MCM-41 composites

Abstract

In this work, iron oxide-mesoporous silica MCM-41 composites were prepared by hydrothermal and impregnation methods, while their adsorption properties were examined by using acetylsalicylic acid as the model of the pharmaceutical pollutant. X-ray diffraction (XRD) patterns and diffuse reflectance ultraviolet-visible (DR UV-vis) spectra showed that the iron oxides (α-Fe2O3) were successfully incorporated into the MCM-41. Field emission scanning electron microscopy (FESEM) micrographs revealed that the composites prepared by hydrothermal synthesis exhibited aggregated plate-like α-Fe2O3 particles, while irregular particles were found in the composites prepared by the impregnation method. The adsorption capacity of MCM-41 was greatly improved upon the introduction of α-Fe2O3. Composites prepared from hydrothermal synthesis displayed excellent adsorption capacity compared to the composites prepared by the impregnation method. This might be due to the better maintained mesostructure of the MCM-41 and the plate-like morphology of the α-Fe2O3, which might tend to expose more active adsorption site. The interactive behaviour between acetylsalicylic acid and the composites can be well described by the Langmuir isotherm model, suggesting that the adsorption of acetylsalicylic acid is monomolecular layer process.